From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id D2A67C433FE for ; Wed, 8 Dec 2021 10:30:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231693AbhLHKeD (ORCPT ); Wed, 8 Dec 2021 05:34:03 -0500 Received: from szxga03-in.huawei.com ([45.249.212.189]:29161 "EHLO szxga03-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231671AbhLHKeA (ORCPT ); Wed, 8 Dec 2021 05:34:00 -0500 Received: from dggpeml500023.china.huawei.com (unknown [172.30.72.54]) by szxga03-in.huawei.com (SkyGuard) with ESMTP id 4J8D046c5czXdZm; Wed, 8 Dec 2021 18:28:20 +0800 (CST) Received: from [10.67.110.112] (10.67.110.112) by dggpeml500023.china.huawei.com (7.185.36.114) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2308.20; Wed, 8 Dec 2021 18:30:26 +0800 Subject: Re: [PATCH -next 1/2] string.h: Introduce memset_range() for wiping members To: Andrew Morton CC: , , , , , , , , , , , , , , , , , References: <20211208030451.219751-1-xiujianfeng@huawei.com> <20211208030451.219751-2-xiujianfeng@huawei.com> <20211207202829.48d15f0ffa006e3656811784@linux-foundation.org> From: xiujianfeng Message-ID: Date: Wed, 8 Dec 2021 18:30:26 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.9.1 MIME-Version: 1.0 In-Reply-To: <20211207202829.48d15f0ffa006e3656811784@linux-foundation.org> Content-Type: text/plain; charset="gbk"; format=flowed Content-Transfer-Encoding: 8bit X-Originating-IP: [10.67.110.112] X-ClientProxiedBy: dggems704-chm.china.huawei.com (10.3.19.181) To dggpeml500023.china.huawei.com (7.185.36.114) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org ÔÚ 2021/12/8 12:28, Andrew Morton дµÀ: > On Wed, 8 Dec 2021 11:04:50 +0800 Xiu Jianfeng wrote: > >> Motivated by memset_after() and memset_startat(), introduce a new helper, >> memset_range() that takes the target struct instance, the byte to write, >> and two member names where zeroing should start and end. > Is this likely to have more than a single call site? There maybe more call site for this function, but I just use bpf as an example. > >> ... >> >> --- a/include/linux/string.h >> +++ b/include/linux/string.h >> @@ -291,6 +291,26 @@ void memcpy_and_pad(void *dest, size_t dest_len, const void *src, size_t count, >> sizeof(*(obj)) - offsetof(typeof(*(obj)), member)); \ >> }) >> >> +/** >> + * memset_range - Set a value ranging from member1 to member2, boundary included. > I'm not sure what "boundary included" means. I mean zeroing from member1 to member2(including position indicated by member1 and member2) > >> + * >> + * @obj: Address of target struct instance >> + * @v: Byte value to repeatedly write >> + * @member1: struct member to start writing at >> + * @member2: struct member where writing should stop > Perhaps "struct member before which writing should stop"? memset_range should include position indicated by member2 as well > >> + * >> + */ >> +#define memset_range(obj, v, member_1, member_2) \ >> +({ \ >> + u8 *__ptr = (u8 *)(obj); \ >> + typeof(v) __val = (v); \ >> + BUILD_BUG_ON(offsetof(typeof(*(obj)), member_1) > \ >> + offsetof(typeof(*(obj)), member_2)); \ >> + memset(__ptr + offsetof(typeof(*(obj)), member_1), __val, \ >> + offsetofend(typeof(*(obj)), member_2) - \ >> + offsetof(typeof(*(obj)), member_1)); \ >> +}) > struct a { > int b; > int c; > int d; > }; > > How do I zero out `c' and `d'? if you want to zero out 'c' and 'd', you can use it like memset_range(a_ptr, c, d); > > > .